Yea 38 watt should be plenty! I reduced from 39 to 26 and they're still doing fine. Except for in the shade, that's where they tend to start to grow vertically. About planting them, I was always a glutton for punishment so i seperated each individual leaf node and planted it. The first time around was with emersed growth, it took quite awhile for it to start sending off runners. The second time (more recently) was after i tore my tank down to remove the microswords and run a pure glosso carpet. It was with horizontal growth glosso with a well developed roots. Planting was fast. The long part was seperating each node again.
Alot of people just plant them in very small bunches and cut runners to head it grow densly.